A nurse auscultates the heart of Anu, a 21-year-old female. Anu seeks a consultation for dizziness and easy fatigability. During assessment, the nurse identifies a mid-to-late systolic click followed with mid-to-late systolic murmur at the cardiac apex. The murmur gets louder when Anu stands up. Based on these findings, Anu is most likely considered for which of the following cardiac problems?